Enabling Highly-Reversible Aqueous Zn-Ion Batteries via 4-Hydroxybenzoic Acid Sodium Salt Electrolyte Additive

Due to the intrinsic safety and cost effectiveness, aqueous Zn-ion batteries (AZIBs) are considered a promising candidate for future energy storage systems. However, the widespread implementation of AZIBs faces significant obstacles due to various undesirable side reactions, including hydrogen evolution reaction (HER), corrosion, and uncontrolled dendrite growth at the anodes. Here, 4-hydroxybenzoic acid sodium salt (PHB) is employed in the ZnSO₄ electrolyte to enable highly-reversible zinc anodes. PHB has a greater tendency to bind with the Zn surface, resulting in increased steric effects within the electrolyte. As a result, it hinders the direct interaction between anode and water while facilitating the uniform plating of Zn²⁺ . Zn/Zn batteries with PHB additives realized more than 1600 h stable cycling life under 1 mA cm^-2 and 1 mAh cm^-2 . Moreover, Zn/Cu batteries with PHB additives achieved a reversible plating/stripping process for over 500 cycles with high average CE of 98.6 %. In addition, the assembled Zn/NH₄ V₄ O₁₀ batteries with PHB additive yielded 80.5 mAh g^-1 after 1000 cycles at 10 A g^-1 . The inexpensive and effective application of PHB as an electrolyte additive has the potential to significantly enhance the stability and dependability of ZIBs.